The present invention relates to a scroll fluid machine, such as a scroll compressor, a scroll vacuum pump, a scroll expander or a scroll blower.
Such a scroll fluid machine comprises a stationary scroll and an orbiting scroll which is supported on an eccentric shaft portion of a drive shaft to turn via a bearing. The stationary scroll comprises, a stationary end plate having a stationary wrap and the orbiting scroll comprises an orbiting end plate having an orbiting wrap. Between the stationary wrap and the orbiting wrap, a sealed chamber is formed and there is a self-rotation preventing device for preventing rotation of the orbiting scroll around its own axis.
With the eccentric shaft portion of the drive shaft and the self-rotation preventing device, the orbiting scroll is eccentrically revolved with respect to a stationary scroll. According to a direction of rotation, fluid sucked through the outer circumference is introduced into the center while being compressed, or fluid sucked from the center is depressurized and discharged from the outer circumference. The stationary and orbiting wraps comprise involute curves which gradually increase around its their center in a direction of rotation or comprise a curve comprising short arcs having a common center and being connected in a circumferential direction or comprise a combination thereof. A radial gap between the stationary and orbiting wraps is exactly determined so that wraps do not to engage with each other and to avoid significant increasing radial size of the gap.